a. Field of the Invention
This disclosure relates to a rotational coupling device for a power transmission assembly. In particular, the disclosure relates to a rotational coupling device having an electromagnet assembly for use in coupling, uncoupling or braking members of the power transmission assembly and in which the electromagnet assembly is held against rotation without requiring mechanical contact between the electromagnet assembly and surrounding structure.
b. Background Art
Rotational coupling devices such as clutches and brakes are used to control transfer of torque between two bodies. In an electromagnetic coupling device, an armature coupled to an input or output member is brought into engagement with, and/or disengagement from, a coupling disc coupled to the other of the input or output members in order to rotatably couple or decouple the input and output members and/or brake one of the members.
In conventional electromagnetic coupling devices, the electromagnet assembly used to establish an electromagnetic circuit between the armature and coupling disc is fixed against rotation by mechanically coupling the housing for the electromagnet assembly to a nearby structure. This mechanical coupling has several disadvantages, however, that arise as a result of engagement between the electromagnet assembly and structure when the mechanical coupling attempts to resist rotation of the electromagnet assembly during operation of the rotational coupling device. First, the engagement between the electromagnet assembly and structure creates undesirable levels of noise. Second, the engagement creates significant mechanical stress and wear on components of the rotational coupling device and the structure.
The inventors herein have recognized a need for a rotational coupling device that will minimize and/or eliminate one or more of the above-identified deficiencies.